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P2 - Physics > Work, Energy and Momentum > Flashcards

Work, Energy and Momentum Flashcards

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1
Q

What is the spring constant of a spring?

A

The force per unit extension needed to stretch it

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2
Q

What happens if a spring is stretched beyond its limit of proportionality?

A

It no longer obeys Hooke’s law

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3
Q

What is Hooke’s law?

A

Force applied = spring constant x extension

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4
Q

Explain what Hooke’s law means?

A

That the extension of a spring is directly propionate to the force applied to it

provided the limit of proportionality is not exceeded

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5
Q

What is elastic potential energy?

A

Energy that is stored in an elastic object when work is being done to the object

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6
Q

What happens when the work being done to an elastic object stops?

A

The elastic energy stored within the object is released

Some transferred as kinetic energy

May make the aroma vibrate more so it becomes warmer

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7
Q

What improvements can be made to help with fuel economy?

A
  • reducing the speed
  • fitting a wind deflector
  • both reduce the air resistance on the vehicle and so reduce fuel use
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8
Q

What does an anti- skid surface do?

A

They increase the friction between a car tyre and the road surface

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9
Q

How can you work out the extension of a spring from :

1 length after stretching
2 original length

A

Spring extension = length after stretching - original length

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10
Q

When is work done on an object?

A

When a force makes it move

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11
Q

Work done = ?

A

Energy transferred

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12
Q

How can you work out the work done from :

1 the force
2 distance moved in direction of the force

A

Work done = Force x distance moved in direction of the force

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13
Q

What is gravitational potential energy?

A

The energy stored in an object because of its position in the Earth’s gravitational field

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14
Q

What does the gravitational potential energy depend on?2

A

It’s weight and how far up it moves vertically

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15
Q

What is the kinetic energy of an object?

A

The energy of that an object has due to its motion

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16
Q

What does kinetic energy depend on?2

A

Mass and speed

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17
Q

What makes an object elastic?

A

If it regains its shape after being stretched or squashed

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18
Q

What is he unit of momentum?

A

Kg m/s

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19
Q

What three things happen when two object push apart? 3

A
  • they move apart
  • with a different speed if they have unequal masses
  • with equal and opposite momentum, so their momentum is zero
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20
Q

What does the force of the impact depend on when two vehicles collide?3

A
  • mass
  • change in velocity (speed)
  • duration of impact (time)
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21
Q

If the impact time is longer what happens to the impact force?

A

The longer the time the less impact force

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22
Q

What is the purpose of crumple zones in a car?

A

They lessen the force of impact by increasing the impact time

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23
Q

What is another way of expressing the effect of an impact on an object?

A

G-force

24
Q

What do seat belts do for you?2

A

They spread the force across the chest

Increase the impact time

25
Q

What do side impact bars do?

A

Give way in an impact so increase the impact time

26
Q

What do we use consecration a of momentum for?

A

Finding the speed of a car before an impact

27
Q

What are electromagnetic waves?

A

Electric and magnetic disturbances that transfer energy from one place to another

28
Q

What speed does electromagnetic waves travel at?

A

300 million m/s

29
Q

What does white light contain?

A

All colours of the visible spectrum

30
Q

The warmer the air the…?

A

Greater the speed of sound

31
Q

How do anti skid surfaces work?

A

They increase the friction between the tyre and the road

The surface is rougher and lighter to make it clear

32
Q

How can fuel economy be improved?

A

By fitting a wind deflector
Reducing the speed

Reduce air resistance — reduce fuel use

33
Q

When an elastic object is stretched what energy is stored in the object?

A

Elastic potential energy

34
Q

When the stretching force is removed hat happens?

A

The elastic energy stored is release

Some of it maybe trad feted into kinetic energy to make objects vibrate more and become warmer

35
Q

How does momentum explain an air bag?

A

Increased time taken for head to stop
Decreased rate of change in momentum (deceleration)
Reduced force on head

36
Q

When is work done?

A

When a force caused an object to move through a distance

37
Q

What is gravitational potential energy?

A

The energy that an object has by virtue of its position in a gravitational field

38
Q

What happens to an objects gravitational potential field strength, when an object is raised?

A

Work is done against gravitational force

So the object gains gravitational potential energy

39
Q

What is momentum measured in?

A

Kg m/s

40
Q

Examples of the conservation of momentum?

A

Collisions

Explosions

41
Q

What is the conservation of momentum?

A

The total momentum before an event is equal to the total momentum after th event

42
Q

What does work done depend on?

A

Size of force

Distance moved

43
Q

What happens to GPE when an object is moved up?

A

It’s gravitational potential energy increases

44
Q

What happens to the GPE when an object moves down?

A

GPE decreased

Decrease in gravitational potential energy is equal to the work done by the force of gravity acting on it

45
Q

What does work done when an object moved up or down depend on?

A

Vertical change in height

It’s weight

46
Q

Unit of momentum?

A

Kg m/s

47
Q

What is effect of the crumple zone?

A

Increases impact time

So lessens impact force

48
Q

How do air bags work?

A

The inflated bag spreads the force of an impact across the upper body of the car
Increases the impact time the effect of the force is lessened

49
Q

What does a seat belt prevent?

A

It stops its wearer from continuing forwards when the car suddenly stops

50
Q

How does a seat belt work?

A

Decelerating force is reduced by wearing a seat belt

The seat belt acts across the chest so it spreads the force out

51
Q

Energy transferred is equal to what?

A

The work done to it

52
Q

How (in terms of forces) do you lift a box from the ground?

A

The force you need to lift an object is equal to the opposite force of gravity
So the upward force needed to apply is EQUAL TO THE OBJECTS WEIGHT

53
Q

What happens to an object when it is moved up?

A

GPE increase

This increase is equal to the amount of work done

54
Q

What happens when an object is moved down?

A

GPE decreases

This decrease is equal to the work done by the force of gravity acting on it

55
Q

How do kinetic recovery systems work?

A

They store energy when a vehicle breaks and uses it later eg to boost speed in Formula 1

56
Q

When a skateboard moves backward, why does the skateboarder move forwards?

A

Momentum before jumping = momentum after jumping

Before momentum of both is zero
After jumping the skateboarder has momentum forwards so the skateboard must have momentum backwards

P2 - Physics (5 decks)

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